Nonair-conditioned structures are generally ventilated and cooled by opening one or more windows. However, the opened windows often admit not only a welcome breeze but the unwelcome din of nearby factories, airports, freeways, and the like.
The use of sound-absorbing drapes over the open window helps somewhat but can significantly impede both air flow and light transmission. Additionally, such drapes often offer little if any resistance to the transmission of sound. More specifically, such drapes are capable of only low absorption. Sound not absorbed within the drapery fabric or reflected from it is readily transmitted through the drape. Acoustical venetian blinds whose slats are constructed primarily of sound absorbent material afford somewhat improved air flow and light transmission characteristics but, like acoustic drapes, are only marginally effective with regard to both absorbing sound and blocking its transmission through the slats themselves.
A different acoustical problem arises in modern air-conditioned structures, such as office buildings, whose exterior rooms have quite large window area-to-wall area ratios. The large (and often fixed) windows now fashionable in such structures present a sound reverberation problem which must often be compensated for by relatively expensive acoustical treatment of the walls and other nonglass surfaces in the room. Because they lack the capability of effectively blocking the transmission of sound, acoustical drapes and blinds are a less than satisfactory solution to this internal sound problem. Although some of the sound generated within the room is absorbed by such drapes and blinds, a significant portion of it is transmitted through such devices, is reflected by the window and retransmitted through the drapes or blinds into the room.
The above-described problems are merely representative of many acoustical problems associated with windows, whether movable or fixed. It can be seen that a need exists for a sound barrier capable of absorbing sound and blocking its transmission yet permitting the passage of air and/or light therethrough when desired. Accordingly, it is an object of this invention to provide a sound barrier which eliminates or minimizes above-mentioned problems.